The field of the invention generally relates to a fan positioned so as to force outside fresh air into a room, and more particularly relates to an electronic controller that automatically controls the operation of such a fan.
Window fans are in widespread usage for blowing outside fresh air into buildings such as residential homes or apartments. Although a window fan does not have a heat exchanger like an air conditioner to cool the air, a fan has a significant advantage in that it is relatively inexpensive to purchase and operate. Also, fans may have a considerable advantage over room air cleaners such as electrostatic cleaners because fans have much higher flow rates. In other words, even though electrostatic cleaners remove particles such as smoke from indoor air, considerable time is required to clear a smokey room because the air flow rate of an electrostatic cleaner is relatively small. A window fan, on the other hand, has a relatively high air flow rate and can clear a room of smoke in a relatively short time period.
One disadvantage of fresh air exchange fans is that their operation must generally be closely monitored and regulated because there are only certain conditions under which operation is advantageous; other times, they will make the inside environment more uncomfortable. For example, during the hot summer months when it is most desirable to use fans, the outside air may be hotter and more humid than the inside air during the mid-portion of the day. This, of course, is especially true if the room is also served by an air conditioner. Accordingly, if a fresh air exchange fan is forcing outside air into the room during the hottest hours of the day, the room will become hotter and more humid. Generally, the proper time for operation of a window fan is later in the day after the inside temperature has climbed above the outside temperature or after it has cooled down outside; then, the outside fresh air can be forced into the room to remove heat that has built up during the day. Also, if an intake fan is operated while it is raining, rain water may be directed into the room.